a-z silent letter rules

Select the set of letters that, when sequentially placed in the blanks of the given letter series, will complete the letter series. Z_P_ _ U _ D Z U _ D

Select the combination of letters that when sequentially placed in the gaps of the given letter series will complete the series. R _ K _ _ Z _ C _ Z K C

The letters skipped between adjacent letters are the order of 1, 2, 3, 4, ..... Which alternative follows this rule.

In one of the series of letters given below adjacent letters are skipped in a decreasing order. Which one of the following series observes the rule given above?

Prefixes|Suffixes|Silent Letters|OMR

Find the rule which gives the number of matchsticks required to make the following matchstick patterns. Use a variable to write the rule. A pattern of letter Z as Z